Broadcast content or the content in packaged media has basically been used at the place at which the content using apparatus or a replay equipment is positioned, or at an equipment connected to the apparatus and the equipment through a home network (hereinafter, also referred to as a “local access (LA)”) in the past. For example, from technical terms related to a communication channel or a codec, it is difficult to use content, with a transmission through an external network such as a Wide Area Network (WAN) by connecting to the above-mentioned content using apparatus or replay equipment from outside with a mobile equipment (hereinafter, also referred to as a “remote access (RA)”). However, a data communication technology such as a Long Term Evolution (LTE) or a World Interoperability for Microwave Access (WiMAX) and a high-compression codec such as the H.264 are expected to become popular so that using the technology or the codec is likely to make a remote access implementable in the future. For example, the user can remotely access the server of user's home on the go in order to replay content.
It is relatively easy to perform an illegal operation on digital content, for example, copy or falsification. Among others, in a remote access, it is necessary to prevent an illegal use in content transmission in order to protect the copyright of the content while permitting the use of the content for a personal or home purpose.
The Digital Transmission Content Protection (DTCP) developed by the Digital Transmission Licensing Administrator (DTLA) is cited as an industry-standard technology relating to protection for a digital content transmission. An authentication protocol between the equipment in a content transmission and a transmission protocol for encrypted content are prescribed in the DTCP. In summary, the prescription includes that a DTCP-compatible equipment does not transmit an easy-to-use compressed content in an unencrypted state out of the equipment, that the key exchange required to decrypt an encrypted content is conducted according to a predetermined mutual authentication and key exchange (AKE) algorithm, and that the range of equipment among which the key is exchanged according to an AKE command is limited.
Further, the DTCP technology that has been ported to an IP network or, namely, a DTCP-IP (DTCP mapping to IP) can circulate digital content also at home through the IP network. The current DTCP-IP (DTCP volume 1 Specification Supplement E Revision 1.2) mainly intends to secure the use of contents only at home and set limitations on the round trip time (RTT) and the hop number of IP routers or, namely, the Time To Live (TTL) for an AKE command.
For example, there is proposed a information communication system for continuing monitoring each received AKE command and continuing updating the maximum value of the TTL value during the period from the time when a Source starts a DTCP-IP authentication until the time just before the Source completes the authentication, and checking the maximum TTL value just before the completion of the authentication process in order to complete the authentication process with exchanging the key when the maximum value is three or less, or in order to complete the authentication process without performing the process in the final phase when the maximum value exceeds three (for example, see Patent Document 1).
Further, the owner of the content can prohibit a content providing apparatus (Source) from transmitting content to many content using apparatuses (Sinks) at the same time in order to restrict an illegal use of the content.
On the other hand, the user who uses the content can separately use a plurality of content using apparatuses depending on the situation, or a family can share a content providing apparatus positioned at home. In such utility forms, a content transmission from a content providing apparatus to a plurality of content using apparatuses at home is in a range of the legitimate use of content. Thus, if the owner of the content limits the number of apparatuses in order to prohibit a content transmission as described above, it follows that the owner unduly restricts the user's use of the content.